Recently, high-order emission control has been applied to diesel engines (hereinafter simply referred to as engines). Accordingly, it has been desired to mount an exhaust gas purifier to purify atmospheric pollutants contained in exhaust gas on a working machine such as a construction civil-engineering machine, an agricultural machine, and an engine generator on which an engine is mounted. As an exhaust gas purifier, a diesel particulate filter (hereinafter referred to as DPF) to collect particulate matter and such substances contained in exhaust gas has been known (see patent documents 1 to 3). Also, as a countermeasure to take against exhaust gas, there has been known a technique of providing an EGR device (exhaust gas recirculation device) to make part of exhaust gas flow back to the intake side. Thus, combustion temperature is suppressed to a low level to decrease an amount of NOx contained in exhaust gas (see patent document 4). These exhaust gas countermeasure devices are electronically controlled utilizing electronic components such as various sensors and controllers in order to effectively implement functions of the exhaust gas countermeasure devices.